


Promises Made

by shadowtraveled (meteorfest)



Category: Percy Jackson and the Olympians & Related Fandoms - All Media Types, Percy Jackson and the Olympians - Rick Riordan, The Heroes of Olympus - Rick Riordan
Genre: Crossovers & Fandom Fusions, M/M, Minor Character Death, Prompt Fic
Language: English
Status: Completed
Published: 2015-10-19
Updated: 2015-10-19
Packaged: 2018-04-27 02:36:13
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,509
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5030395
Author URL: https://archiveofourown.org/users/meteorfest/pseuds/shadowtraveled
Summary: <blockquote class="userstuff">
              <p>As Percy and Nico fight Kronos’ Heartless in the throne room of Olympus, Will and Mitchell are sent to guard the Door to Kingdom Hearts. A PJO/Kingdom Hearts AU. Written for rarepairproject.</p>
            </blockquote>





	Promises Made

**Author's Note:**

  * For [Allarica](https://archiveofourown.org/users/Allarica/gifts).



> Set in the same universe as my other Kingdom Hearts AU, but this is a different story altogether, so I'm posting it on its own. For Allarica because she helps me plot this AU and I have no regrets for writing this part first.

It was the final struggle between the demigods of Camp Half-Blood and the Heartless, led by Kronos, the Titan Heartless that had possessed one of their own, a son of Hermes, Luke Castellan. Some demigods said Luke had let Kronos possess him, others said it was done against Luke’s will. No one knew what to believe, really. All they knew was that Luke was lost to them, Kronos in control of the demigod’s body and using it now to attack Mount Olympus, intending to destroy the Keyhole in the throne room.

There was a group of demigods already on Olympus, led by Percy Jackson, one of the Keybearers that had been chosen to defend Camp Half-Blood and Olympus. Having already locked the Keyholes in the Sea of Monsters and in the Labyrinth, Percy had quickly become a great hero in the camp and was looked up to by most of the demigods there. So when he’d taken charge of the assault against the Titan army, most of them had readily followed his orders.

Three other Keybearers were with Percy on Mount Olympus - Nico di Angelo, wielder of the Oblivion; Mitchell Reddy, bearing the Crown of Guilt; and Will Solace, carrying the Aubade. The plan was that the four of them would split up on Olympus. Percy would lead the charge against Kronos, with a handful of other demigods as back up. Nico would be taking up the defense outside the throne room to keep any of Kronos’ minions from getting in.

Will and Mitchell had an important job to do. Somewhere on Olympus, Hestia had told Percy, was the Door to Kingdom Hearts, the heart of all worlds. She’d warned Percy that, if Kronos succeeded in destroying the Olympus Keyhole, his next target would be Kingdom Hearts itself. Taking the goddess’ advice, Percy had assigned Will and Mitchell to find and guard the Door.

So that’s what they were doing. It was no easy task, as Olympus had gone dark, with all the Olympians locked away, save for Hestia, who still guarded her flame. The darkness gave way to Heartless by the dozen, Shadows and Soldiers leaping out to try to stop Mitchell and Will from their task. Keyblades swung, magic burst, and potions were shared to make the trek across the home of the gods. Neither Will nor Mitchell were particularly adept fighters, both of them heavily reliant on magic to supplement their attacks, but they made their way around together.

They eventually found the Door, after scouring every part of Olympus. Following the advice of one of the minor deities - a young man who had once been a mortal demigod like them - Will led Mitchell into a cavern on the mountain It had been guarded at one point, if the discarded weapons outside were anything to judge by, but the guards were gone. Will took Mitchell’s hand and the two of them went inside, following the path, guided only by the glow of Will’s golden Keyblade.

At the end of the path, in a deep cavern, stood a large double door. White panels accentuated with diamond-shaped stained glass window stretched high above the two demigods as Will and Mitchell approached the Door. Looking at it, Mitchell could hardly believe that this door, so simple and innocuous, was the Door that Kronos would use to destroy Western Civilization and begin a new age of his own design.

“Kind of seems like it doesn’t fit the hype, does it?” Will asked as he looked up at the Door. “It doesn’t _look_ like it’s potentially world-threatening.”

Mitchell stepped forward towards the Door, placing one gloved hand on its surface. “No, it doesn’t,” he murmured. “That’s what makes it scary, isn’t it?”

Will nodded. “Guess so. We’ll have to make sure Kronos can’t use it.” He hefted his Keyblade up and turned his back on the Door, readying himself in case any Heartless, or Kronos himself, broke into the cavern to attack. “Hopefully, Percy and the others have a handle on everything on the surface.”

“Hopefully,” Mitchell murmured. He raised his own Keyblade and shifted his position.

For a while, it seemed like everything was probably going well on the surface. No Heartless had breached the cavern yet, leaving Will and Mitchell alone in silence. Mitchell eventually broke the silence, just unable to stand still for so long in the quiet without speaking. He was beginning to get nervous and when he was nervous, he had to speak up to calm his mind. He asked Will what he planned to do when this war was over, if he was going to stay at camp for a while or if he was going to go home to his mortal family.

Mitchell had known Will for a couple of years now, ever since the first summer he’d been at Camp Half-Blood. Will had gotten to camp for the first time only a few days before Mitchell, staying in the Hermes cabin for a single night before being claimed by Apollo. Mitchell had barely been in the Hermes cabin for a few hours before Aphrodite had claimed him. The two of them had spoken a few times that first summer, though it seemed like they hadn’t really gotten to know each other until the summer after.

Mitchell alternately blamed and thanked his sister, Silena, for giving him a push towards Will, having picked up on the crush that Mitchell was only beginning to realize he had on the older demigod. His sister had dragged him to a small group game of Spin the Bottle and, he would swear by their mother that Silena had rigged the game, the bottle had pointed directly at Will when it was Mitchell’s turn. It had been Mitchell’s first kiss and he suspected that it was Will’s, too. Will had been nervous about it and the kiss had been pretty chaste, but Mitchell hadn’t forgotten it.

Will hadn’t talked about it after, though, so Mitchell was left wondering if it meant anything for the son of Apollo or if it had just been a game.

He thought about asking Will about it now, while he had the chance, with it just being the two of them, but as he opened his mouth to speak up again, there was a sudden, lurching earthquake. The cavern ceiling shook and stalactites cracked free from their bases and began plummeting from the ceiling. Will lunged towards Mitchell, shoving the other boy out of the way of a falling stalactite, casting a quick Barrier to protect the two of them as he slipped his arm around Mitchell’s waist.

Mitchell found himself blushing as they hit the ground, Will on top of him as his Barrier kept them from getting injured by falling debris. He looked up to Will as the son of Apollo pushed himself up. Worried blue eyes peeked out under Will’s blond bangs as the older demigod looked back down at Mitchell.

“Are you alright?” Will asked.

“Y-yeah, I’m fine,” Mitchell replied. He tilted his head up towards the cavern ceiling, his golden-brown eyes widening as he caught sight of a giant Heartless above them. “Oh my gods. Is that…Kronos?”

Will followed Mitchell’s line of sight and a soft curse escaped his lips. “Looks like we’re joining the fight.”

* * * * *

Kronos wasn’t going to go down that easily. It took all for Keybearers to weaken him, Percy and Nico taking the offensive while Will and Mitchell backed them up with magic support and healing spells. Kronos refused to give up, though. Still mostly confined to Luke’s body, with a symbiotic Heartless Guardian protecting his weaker form, the Titan was eventually subdued, but he still would not give in to the Keybearers.

“Foolish demigods!” Kronos bellowed. He unleashed a wave of force, knocking all four of them back. Darkness gathered around him and his symbiote grew in size. “You will not stop me! Your powers are no match for the power I will be granted.” He stood, forcing Luke’s body past its limits as he raised his arms, golden eyes falling on the Door standing in the cavern. “Kingdom Hearts! I command you! Fill me with the power of Darkness!”

The Door, much to the shock of all the Keybearers, began to open. A loud groan echoed through the cavern from the Door as it opened for the first time in who knew how long. Kronos began to laugh, a sinister sound that struck at the heart. Mitchell reached for Will’s hand, grasping it as he stared at the Door.

 _This can’t be the end!_ Mitchell thought, terrified. He gripped at Will’s hand and, though it was little reassurance, he felt Will squeeze back. _It can’t end like this!_

“Luke!” Annabeth darted into the cavern from the entrance Will and Mitchell had taken. Though the daughter of Athena had no Keyblade, only her dagger, she wasn’t going to let that stop her. She leapt at Luke, dagger drawn. “Fight him, Luke! You promised! _Family_ , Luke!”

Mitchell had no idea what Annabeth was on about, but he knew that she had once been close to Luke. She’d always been adamant about trying to save the son of Hermes, defending him even as the rest of camp lost their faith in him. Mitchell had come to camp after Luke’s initial betrayal, so he never knew anything more than what he heard through Silena. Whatever Annabeth’s relationship with Luke before, her words now seemed to break through the hold Kronos had on him -

\- if only for a short moment.

Kronos threw Annabeth back and the girl’s dagger clattered to the cavern floor. The Titan began to laugh again. “Promises are made to be broken, Annabeth Chase!” he declared. “The only promise I keep is the promise to destroy you all!”

Kronos took a step towards the Door, then froze. Silence fell in the cavern, Kronos’ laughter cut off suddenly. For a moment, no one had any idea what was going on. The five demigods all held their breath, none of them daring to make a move. Kronos seemed to be struggling to move and the next words out of his mouth gave the reason why.

“You’re wrong,” Luke spoke aloud. It was definitely Luke’s voice, not Kronos’. “About promises…about Kingdom Hearts…” Luke slowly extended one arm, reaching for the dagger on the floor. Kronos wouldn’t let him kneel for it. “Kingdom Hearts…is _Light_!”

The Door suddenly flew open and the entire cavern was flooded with a brilliant white light. Kronos cried out, blinded, while the rest of those in the cavern covered their eyes.

“Percy, I can’t reach…” Luke called out to the demigod closest to him. “The knife!”

Mitchell couldn’t see anything for all the light in the cavern. He had no idea what was going on. He kept his hand in Will’s, holding tight to the other boy. If they survived this, he decided, he was going to tell the son of Apollo how he felt.

A scream of pain and rage rang out suddenly and Mitchell felt a blast of energy knock him back. He lost his grip on Will’s hand and he called the other boy’s name. The light from the Door died after a moment and Mitchell could finally see again.

Luke lay on the cavern floor. The symbiote Heartless was gone, all sign of Kronos gone. Blood pooled under the son of Hermes. Percy and Annabeth both knelt by Luke. Will was just a few feet away from Mitchell, looking around the cavern. Mitchell looked around himself and knew something was wrong.

There were only four demigods in the cavern, where there should be five.

“Nico!”

Mitchell and Will both ran for the open Door. On either side of the double doors, the two of them looked inside. It was dark inside, the only light they could see on the horizon. In the distance, they could see the silhouettes of several Darkside Heartless inside the Door. And, peering closely, Mitchell could see the form of the son of Hades in the distance, his Keyblade in hand.

Will started to go inside. Mitchell grabbed his hand. “Will, no!”

“Someone has to help him,” Will told the other boy. “Mitchell, he can’t fight all those Heartless on his own.”

“Will! Mitchell!” Percy called from behind them. “Quick, we need to close the Door!”

Mitchell didn’t want to close the door. Nico was in there and Will was going to go in to help the other demigod. “Will, please,” he pleaded. “You can’t go in there. The Door - ”

Will bit his lip and let his gaze fall on the doors. “We have to close it together,” he told Mitchell. He pulled his hand out of Mitchell’s and stepped through to the other side, turning around and grabbing the edge of the door. “Together, Mitchell.”

Mitchell’s heart pounded in his chest. Will meant to close the Door from the other side. He was willingly letting himself be locked in the Realm of Darkness. “You can’t - ”

Will leaned towards Mitchell suddenly, pressing his lips to the other boy’s. Mitchell froze, his hand gripping to the Door as Will kissed him. It wasn’t the same chaste kiss that Will had given him before. This kiss was more poignant, carried so much more feeling. It was an admittance, that Will liked him, that he probably hadn’t forgotten that first kiss, that it hadn’t just been a game. Mitchell leaned into the kiss, deepening it slightly and letting his own feelings flow into it.

Will held the kiss for a long moment, until Percy shouted at them to hurry. The son of Apollo brought his free hand up to touch Mitchell’s cheek for a moment. “We’ll find a way out. I swear by my father’s lyre.”

“Will…”

“Come on, Mitchell,” the other boy prompted. He gripped to the Door again. “Together we can do it.”

Mitchell wanted to cry. Closing the Door would have been hard enough, but then Will _had_ to go and kiss him first. How could he just close the Door and let Will be locked in the Realm of Darkness? Even if Will swore to find a way out, to get himself and Nico back, how long would it take? Would he succeed?

“Mitchell.”

Mitchell fought back the tears and pressed his hands against the Door. He lifted his head and locked his eyes with Will’s. “Promise me!”

Will nodded, gripping to the Door. “I’ll come back to you, I promise!”

Between the two of them, with Will pulling and Mitchell pushing, the Door slowly closed. Mitchell peeked through the crack of the Door at the last moment and caught a smile on Will’s lips, proud and heartbroken at the same time. Those lips parted for one last message, but the Door clicked shut before Will could speak. The last words Mitchell knew from the son of Apollo was his promise to come back.

Mitchell fell to his knees in front of the Door, one hand against it. “I know you will.” 


End file.
